The interest of our laboratory center on the biology of the lymphoid system and its derivative cell types. The long term goal of these studies is the understanding of the molecular basis of immune phenomena. We propose to isolate the immunologically active component(s) of "Transfer Factor" and characterize them chemically. Donors who are highly sensitivie to a variety of bacterial and/or fungal antigens will be employed as sources of "Transfer Factor." This material will be fractionated by a combination of gel filtration, isoelectric focusing and gel electrophoresis. Assays of the fractions so obtained will be carried out in vivo and in vitro. An attempt will also be made to design an appropriate animal system for such studies.